The invention relates to melt-processable, highly-neutralized ethylene, C3 to C8 xcex1,xcex2 ethylenically unsaturated carboxylic acid copolymers and process for making them. It relates to such copolymers, neutralized to greater than 90%, particularly to those neutralized to nearly to or to 100%. These copolymers are made by incorporating a sufficient amount of specific organic acid (or salt) into the copolymer before neutralization to the high level. These copolymers are useful in making molded products such as golf ball components, thermoplastic shoe soles for cleated footwear, and resilient foams for sporting goods.
Ionomers of acid copolymers of alpha olefins, particularly ethylene, and C3-8 xcex1,xcex2 ethylenically unsaturated carboxylic acid, have been known for a long time. U.S. Pat. No. 3,264,272 (Rees) teaches methods for making such inonomers from xe2x80x9cdirectxe2x80x9d acid copolymers. xe2x80x9cDirectxe2x80x9d copolymers are polymers polymerized by adding all monomers simultaneously, as distinct from a graft copolymer, where another monomer is grafted onto an existing polymer, often by a subsequent free radical reaction. A process for preparing the acid coploymer on which the ionomers are based is described in U.S. Pat. No. 4,351,931.
The acid copolymers may contain a third softening monomer such as an alkyl acrylate or methacrylate. The ethylene acid copolymers can be described as an E/X/Y copolymers where E is ethylene, X is the xcex1,xcex2 ethylenically unsaturated carboxylic acid, particularly acylic and methacrylic acid, and Y is a softening comonomer such as a C1 TO C8 alkyl acrylate or methacrylate ester. X and Y can be pent in a wide range of percentages, X typically up to about 35 weight percent (wt. %) of the polymer and Y typically up to about 50 weight percent of the polymer.
The wide range of neutralization of the acid moiety in the acid copolymer by a wide range of cations is known. Typical cations include lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, and combinations of such cations. Neutralization to 90% and higher, including up to 100%, is known, but there remains a need to achieve such a high degree of neutralization without loss of melt-processability or properties such as elongation and toughness. This is particularly so for copolymers with high acid levels and when using cations other than barium, lead and tin to neutralize the copolymer.
It has been found that, by modifying an acid copolymer or ionomer with a sufficient amount of specific organic acids (or salts thereof); it is possible to highly neutralize the acid copolymer without losing processability or properties such as elongation and toughness. The organic acids employed in the present invention are aliphatic, mono-functional, saturated or unsaturated organic acids, particularly those having fewer than 36 carbon atoms.
The thermoplastic composition of this invention consists essentially of (a) aliphatic, mono-functional organic acid(s) having fewer than 36 carbon atoms; and (b) ethylene, C3 to C8 xcex1,xcex2 ethylenically unsaturated carboxylic acid copolymer(s) and ionomer(s) thereof, wherein greater than 90%, preferably near 100%, and more preferably 100% of all the acid of (a) and (b) are neutralized.
With the addition of sufficient organic acid, greater than 90%, nearly 100%, and preferably 100% of the acid moieties in the acid copolymer from which the ionomer is made can be neutralized without losing the processability and properties of elongation and toughness.
The melt-processable, highly-neutralized acid copolyrner ionomer can be produced by
(a) melt-blending ethylene a,d ethylenically unsaturated C3-8 carboxylic acid copolymer(s) or ionomer(s) thereof that are not neutralized to the level that they have become intractable (not melt-processable) with one or more aliphatic, mono-functional, saturated or unsaturated organic acids having fewer than 36 carbon atoms or salts of the organic acids, and then
(b) Adding a sufficient amount of a cation source to increase the level of neutralization all the acid moieties (including those in the acid copolymer and in the organic acid) to greater than 90%, preferably near 100%, more preferably to 100%.